What game interpreter were you thinking about using? The original PQ1 used AGI, however you could use the resources from PQ1 and remake it into an SCI game (similar to what Cloudee did with Black Cauldron). I have no experience with AGI games (and still in the beginning learning stages with SCI), however on the surface, the engines seem very similar.
You seem to be on the right track with your initial thoughts: I'd think a map would be a room, and the vehicle would be the ego.
There are lots of sites out there for playing Sierra-style games, but much fewer dedicated to programming them. It's worth checking out the AGI discussions on this board (and several others, I'd imagine) for an idea of the current state of the AGI programming community. As for the SCI programming community, this site sure seems to be it (someone please correct me if I am wrong).
Given enough time I'm sure your efforts will pay off...